Part of the interior of Giannikou's laterna — an old Greek instrument that had faded out of use by World War II. It's something akin to an upright player piano, with thousands of little nails pinned into a small cylinder in its base. Each nail activates the strike of a string, creating one played note.

Now based in New York, Giannikou is originally from Athens. She was introduced to Kronos by another of the quartet's longtime collaborators, composer Osvaldo Golijov, who was one of her mentors at the Sundance Film Music program. Giannikou and Kronos spent several years discussing their collaboration before the world premiere of her Strophe in Antistrophe this Friday.

Vocalists Abena Koomson and Sahr Ngaujah — who starred in the off-Broadway and Broadway productions of FELA!, the musical based on the life of Nigerian Afrobeat pioneer Fela Kuti — join Kronos to rehearse the iconic Fela song "Sorrow, Tears and Blood."

Recently, I've been reading a lot about hyperpolyglots: freakishly talented, assiduously hardworking and wonderfully curious individuals who, usually by choice rather than because of geographic, cultural or familial circumstances, learn a whole bunch of languages — a dozen, 37 or 60 of them — just for the sheer joy of communication.

I think those linguistic superstars who can switch tongues with such ease and pleasure have musical kin in the Kronos Quartet. Founded 40 years ago by first violinist David Harrington, the quartet's current lineup also includes longtime second violinist John Sherba and violist Hank Dutt, who both became Kronos members in the late 1970s, along with cellist Sunny Jungin Yang, who just joined the group in June. Over the course of about 40 studio albums — an average of one per year — Kronos has trekked musical and physical terrain all over the globe, from world premieres of music by Steve Reich and Terry Riley to collaborations with artists from Nubian oud virtuoso Hamza El Din to Canadian Inuk throat singer Tanya Tagaq. (I wrote the liner notes for one of their internationally focused albums, 2009's Floodplain.)

Just as with hyperpolyglots, Kronos switches musical idioms as the result of intense work and dedication. So as the group geared up for a five-day residency at the Lincoln Center Out of Doors festival — encompassing 28 concerts and events, 12 premieres, and seven collaborations between Kronos and other artists — photographer Polina V. Yamshchikov and I visited Kronos Tuesday at some of the rehearsals leading up to these performances.

Part of the fascination lay in watching the four slip in and out of styles as easily as other people would change coats. The first rehearsal we attended was with Greek composer, multi-instrumentalist and singer Magda Giannikou, whose Strophe in Antistrophe veers between regions as diverse as Brazil and Asia Minor and which will receive its world premiere Friday evening.

After a brief break at rehearsal, it was time to switch gears entirely for a session celebrating the music and legacy of Afrobeat visionary Fela Kuti in advance of last night's world premiere of the Red Hot + FELA LIVE! project. Kronos worked through Fela's "Sorrow, Tears and Blood" — an iconic, searing indictment of African military regimes of the 1970s — with singers Sahr Ngaujah and Abena Koomson, two stars of the musical Fela!

Afrobeat isn't Kronos' native tongue, and there was less interaction between the quartet and Ngaujah and Koomson during this rehearsal than in the previous session we'd attended with Giannikou, but the six collectively found their way into the music's groove, helped along by Red Hot + FELA LIVE!'s musical director, Stuart Bogie.

Kronos found a more easeful pairing with the band Superhuman Happiness (comprised of members of Antibalas, tUnE-yArDs and Iron and Wine) in a suite of music from the Academy Award-nominated AIDS documentary How to Survive a Plague, whose music was written by Bogie, fellow Superhuman Happiness member Luke O'Malley and late composer and cellist Arthur Russell. The suite's eerie textures and snaking melodies suited this set of collaborators beautifully, as you can hear from the performance itself, recorded live Wednesday night at Lincoln Center Out of Doors.

With special thanks to the Lincoln Center Out of Doors Festival for providing the audio of last night's live performance.